linux-kernel - RE: mcs7830 usb net: "scheduling while atomic" danger?

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Message-ID: <ED3036A092A28F4C91B0B4360DD128EA35987814@shzsmsx502.ccr.corp.intel.com>
Date:	Tue, 19 Jan 2010 10:53:11 +0800
From:	"Du, Alek" <alek.du@...el.com>
To:	Arnd Bergmann <arnd@...db.de>, Julia Lawall <julia@...u.dk>
CC:	Andreas Mohr <andi@...as.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg KH <greg@...ah.com>,
	"Pan, Jacob jun" <jacob.jun.pan@...el.com>,
	Alan Stern <stern@...land.harvard.edu>
Subject: RE: mcs7830 usb net: "scheduling while atomic" danger?

I confirm that thing is bad, I need to prepare another patch to fix that.

Thanks,
Alek
>-----Original Message-----
>From: Arnd Bergmann [mailto:arnd@...db.de]
>Sent: Tuesday, January 19, 2010 5:24 AM
>To: Julia Lawall
>Cc: Andreas Mohr; linux-kernel@...r.kernel.org; Greg KH; Du, Alek; Pan, Jacob
>jun; Alan Stern
>Subject: Re: mcs7830 usb net: "scheduling while atomic" danger?
>
>On Monday 18 January 2010, Julia Lawall wrote:
>> On Mon, 18 Jan 2010, Andreas Mohr wrote:
>> >
>> > Forgive me, but doesn't that mutex_lock()/msleep() (ab)use mean
>> > risking a "scheduling while atomic"?
>> > (such as discussed in e.g.
>> > http://search.luky.org/linux-kernel.2004/msg92817.html )
>> >
>> >
>> > And, if that is the case, shouldn't all such cases simply be killed for
>> > good via a capable semantic patch?
>>
>> The semantic match shown below finds 55 matches.  All but two involve
>> mutex_lock.  Those are in the file
>> /var/linuxes/linux-next/drivers/usb/host/ehci-hub.c
>> in the functions ehci_bus_suspend and ehci_hub_control.
>
>That code looks indeed broken as was added las July as part of 331ac6b288d9
>"USB: EHCI: Add Intel Moorestown EHCI controller HOSTPCx extensions and
>support phy low power mode". The reason that this hasn't triggered is
>probably the lack of Moorestown machines in the field.
>
>	Arnd
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